AU2001268746A1

AU2001268746A1 - Combination of a vacuum interruption device and oil-filled transformer

Info

Publication number: AU2001268746A1
Application number: AU2001268746A
Authority: AU
Inventors: William J. Book; David A. Reinke
Original assignee: ABB Power T&D Co Inc
Current assignee: ABB Inc USA
Priority date: 2000-05-23
Filing date: 2001-05-21
Publication date: 2001-12-03
Also published as: CA2410703A1; WO2001091151A1; CN1439165A; BR0111026A; MXPA02011566A; DE10291282T5

Description

COMBINATION OF A VACUUM INTERRUPTION DEVICE AND OIL-FILLED TRANSFORMER

Field of The Invention:

The present invention relates to a system and method for interrupting current to an electrical transformer device or to an electrical distribution system which is fed through the electrical transformer device. More specifically, the present invention relates to the combination of an electrical transformer device and a magnetically-actuated vacuum interruption device that controls power to, or through, the transformer device.

Background of the Invention Generally, electrical power interruption devices provide overload protection to various types of loads. When interrupting current to an inductive load, an electrical arc often forms between the separating contacts of the interruption device. Depending on the particular application, the electrical arc can cause damage to surrounding components. In the context of an electrical distribution transformer, the electrical arc caused by its proximate interruption device can damage the transformer's windings, causing the transformer to malfunction or fail completely.

In an electrical distribution transformer, loadbreak switching and common fuses use an insulating fluid to extinguish the electrical arc during current interruption. In particular, the transformer's core and windings, and the interruption device (e.g., switch, circuit breaker or fuse) are submersed in a tank of insulating fluid. When the current interruption device disconnects current to the transformer's windings due to an overload or fault condition, for example, the resultant electrical arc is quenched by the surrounding insulating fluid. The same is true where the current interruption device, located within the electrical distribution transformer, is not being used to protect the transformer's windings, but instead is used to protect the downstream portion of the distribution system as it passes through the transformer housing (i.e., "loop-thru" connection). Historically, the insulating fluids have included mineral oil, silicone and sulfur hexaflouride (gas).

Although these arc-quenching fluids have been effective in preventing damage to the distribution transformer's components, their effectiveness often diminishes over time. This diminished capacity results from a breakdown of the fluid's insulating qualities as a result of the many electrical arcs it must quench. As a result, either the insulating fluids or the entire transformer system must be replaced at certain intervals, causing expensive system downtime. Another limitation of these insulating fluids is the gas generated during the arc-quenching process. The resultant gas increases system pressure, often requiring venting of the transformer enclosure. Therefore, it would be advantageous to provide a system and method that interrupts current in an electrical transformer device without causing an electrical arc within the insulating fluid.

Summary of the Invention

The present invention describes a device and method for interrupting electrical power to an electrical transformer winding or to an electrical distribution system downstream from the device. The device comprises at least one electrical transformer winding and at least one interrupting device coupled to the electrical transformer winding. The interrupting device includes a vacuum enclosure. Contacts located in the vacuum enclosure are connected in series with the electrical transformer winding and are movable between an open and a closed position. A linear shaft, coupled to one of the contacts and movable by a magnetic actuator, cause the contacts to move from the closed position to the open position. The magnetic actuator is activated by an input signal, which may be an electrical current or an electrical voltage. By interrupting the electrical current in a vacuum enclosure, the present invention reduces the damage caused by the resultant electrical arc to the electrical transformer system, without significant harm to the insulating fluid.

Brief Description of the Drawings

Other features of the invention are further apparent from the following detailed description of presently preferred embodiments of the invention taken in conjunction with the accompanying drawings, of which:

Figure 1 is aperspective view ofan electrical power distribution transformer device, according to the present invention;

Figure 2 is a zoomed-in view of the perspective view of Figure 1; Figure 3 is a cross-sectional view of a vacuum interruption device, according to the present invention;

Figure 4A is a cross-section view of the vacuum interruption device in a closed position; and

Figure 4B is a cross-section view of the vacuum interruption device in aa open position.

Detailed Description of the Preferred Embodiment

Figure 1 is a perspective view of a three-phase pad-mounted electrical distribution transformer 100, according to the present invention. Electrical distribution transformer 100 may be any suitable transformer, such as a transformer for reducing a relatively high voltage (e.g., 7200 volts) to a relatively low voltage (e.g., 220 volts or 120 volts). Electrical distribution transformer 100 includes a tank 101. Tank 101 may have any suitable construction, such as welded joints and gasketed component seals. Electrical distribution transformer 100 is shown in Figure 1 with the top portion removed for clarity, however, it should be appreciated that electrical distribution transformer 100 is enclosed on all sides.

Tank 101 contains a fluid bath 102. Fluid bath 102 may include any conventional mineral oil, silicone oil, sulfur hexaflouride, or similar substance used to insulate and cool transformer windings 103-105 immersed in tank 101. Vacuum interruption devices 106-108 are mounted to the interior of tank 101, and submerged in fluid bath 102. Each of vacuum interruption devices 106-108 switch one phase of three- phase electrical distribution transformer 100. Electrical busbars 109-111 extend from vacuum interruption devices 106-108, respectively, to a front-side 112 of electrical distribution transformer 100. Electrical busbars 109-111 may be solid metal bars or cable/wire devices. Each of electrical busbars 109-111 attach to high voltage bushings

113-115, respectively. High voltage input power enters electrical distribution transformer 100 via high voltage bushings 113-115. Electrical busbars 109-111 then carry the high voltage input power from high voltage bushings 113-115 to vacuum interruption devices 106-108, respectively. If vacuum interruption devices 106-108 are closed (as discussed further with reference to Figure 4A), the high voltage input power is provided to windings 103-105 of electrical distribution transformer 100. If, on the other hand, vacuum interruption devices 106-108 are open (as discussed with reference to Figure 4B) high voltage input power is prevented from entering windings 103-105 of electrical distribution transformer 100.

Alternatively, electrical distribution transformer 100 and vacuum interruption devices 106- 108 may be used as a "loop-thru" circuit interrupter. In this case, electrical distribution transformer 100 and vacuum interruption devices 106-108 provide protection for electrical current that enters and exists transformer 100 without passing through windings 103-105. In order to make the "loop-thru" connection, electrical distribution transformer 100 uses high voltage input bushings 113-115 and a correspondingly similar set of high voltage output bushings (not shown). All of the high voltage bushings are mounted to front side 112 of electrical distribution transformer 100. Electrical power enters high voltage input bushings 113-115 and passes through vacuum interruption devices 106-108 to the set of high voltage output bushings (not shown). The connection between vacuum interruption devices 106- 108 to the set of high voltage output bushings (not shown) may exist along with the connection between vacuum interruption devices 106-108 and windings 103-105. This set of high voltage output bushings may then be coupled to the remainder of the power distribution system, located downstream from electrical distribution transformer 100. In this way, vacuum interrupting device 106 protects and switches the downstream portion of the distribution system fed through the electrical distribution transformer 100, and not just windings 103-105.

Figure 2 is a zoomed-in depiction of the perspective view of Figure 1. Figure 2 provides greater detail of vacuum interruption device 106 in electrical distribution transformer 100. As shown in Figure 2, vacuum interruption device 106 is connected to an interior rear side 203 of tank 101 by a top end plate 201 and a bottom end plate 202. Top end plate 201 and bottom end plate 202 are insulated from vacuum interruption device

106 and its electrical connections. Busbar 109 extends from vacuum interruption device 106 to front side 112 of electrical distribution transformer 100. Busbar 204 extends from vacuum interruption device 106 to transformer winding 103.

In operation, high voltage power enters bushing 113 (as shown inFigure 1), passes through busbar 109, vacuum interruption device 106_> busbar 204 and into transformer winding 103. If, however, vacuum interruption device 106 is open, high voltage power will be prevented from entering transformer winding 103 , thus de-energizing electrical distribution transformer 100.

Figure 3 is a cross-sectional view of vacuum interruption device 106, according to the present invention, and shows the operation of vacuum interruption device 106 in greater detail. As shown in Figure 3, vacuum interruption device 106 includes a spring 301 connected to a magnetic actuator 306. Magnetic actuator 306 is connected to a control device 302, that activates magnetic actuator 306 remotely. A current or voltage transformer 312 is coupled to an input current 313, and between control device 302 and busbar 109. If a current transformer is selected it may be a ring-style current transformer, well known to those in the art, and mounted on front-side 112 of electrical distribution transformer 100 around high voltage input bushing 113 (as shown in Figure 1). If, on the other hand, a voltage transformer is selected it may be mounted inside tank 101 (as shown in Figure 1). Magnetic actuator 306 is connected to a housing 307. Top end plate 201 is located between magnetic actuator 306 and housing 307, and bottom end plate 202 is attached to the opposite end of housing 307. Top end plate 201 and bottom end plate 202 permit vacuum interruption device 106 to be mounted to electrical distribution transformer 100.

Magnetic actuator 306 is mechanically coupled to an insulated pushrod 303. Insulated pushrod 303 provides dielectric clearance between vacuum interrupter 310 and magnetic actuator 306. A moveable shaft 311 is coupled to insulated pushrod 303. A flexible lead mount 304 is connected to moveable shaft 311. A flexible connector 308 is coupled to flexible lead mount 304. Flexible connector 308 passes through housing 307 and is coupled to busbar 109 via a terminal 309. Flexible connector 308 and flexible lead mount 304 allow an electrical connection between a moving part (i.e., moveable shaft 311) and a stationary part (i. e., busbar 109). Moveable shaft 311 passes through flexible lead mount 304 and into vacuum interrupter 310. A metal bellow (not shown) seals vacuum interrupter 310, while permitting moveable shaft 311 to move freely with the motion of insulated pushrod 303. Vacuum interrupter 310 is connected to busbar 204. Busbar 204 may then be connected either to transformer winding 103, a high voltage output bushing 315, or both. All of the following are located within housing 307: insulated pushrod 303, flexible lead mount 304, flexible connector 308, vacuum interrupter 310, and moveable shaft 311.

In operation, when vacuum interrupter 310 is in a closed position, busbar 109 conducts high voltage power through terminal 309 and on to flexible connector 308. Flexible connector 308 then conducts the high voltage power through vacuum interrupter 310 and onto busbar 204. Busbar 204 conducts the high voltage power either to transformer winding 103, high voltage output bushing 315 , or both. When an overload or fault condition occurs, the condition is sensed by a current or voltage transformer 312. The output of current or voltage transformer 312 is monitored by control device 302. Based on logic programmed within control device 302, when control device 302 notices an overload condition from current or voltage transformer 312, a signal 314 is sent to magnetic actuator 306. Signal 314 may be a current or voltage-based signal. As discussed further with reference to Figures 4A and 4B, signal 314 then causes magnetic actuator 306 to either open or close vacuum interrupter 310.

Figures 4A and 4B are cross-section views of .vacuum interrupter 310, in a closed and opened position, respectively. As shown in Figures 4A and 4B, vacuum interrupter 310 includes moveable shaft 311 coupled to movable contact 401, and a stationary contact 402 coupled to busbar 204. Moveable contact 401 freely moves in a downward direction shown by arrow 404, and in an upward direction shown by arrow 405. Vacuum interrupter 310 is a sealed device containing an evacuated interior 403. Evacuated interior 403 of vacuum interrupter 310 provides an environment by which the arc drawn between moving contact 401 and stationary contact 402 can be controlled. Vacuum interrupter 310 may be a commercially available vacuum interrupter, for example, part no. VG5 manufactured by ABB. As discussed generally with reference to Figure 3, when current or voltage transformer 312 coupled to control device 302 senses a current overload condition, insulated pushrod 303 is moved, causing vacuum interrupter 310 to open and prevent the flow of current into transformer winding 103. As shown in Figure 4A, when signal 314 is sent by control device 302 to close vacuum interrupter 310, magnetic actuator 306 moves moveable shaft 311 in a downward direction 404, compressing spring 301 (as shown in Figure 3), and thus moving contact 401 to connect to stationary contact 402. This action completes the circuit between busbar 109 and transformer winding 103, or between busbar 108 and high voltage output bushing 315, or both. Stationary contact 402 and moving contact 401 are held together (i.e., closed) by high power permanent magnets (not shown) contained within magnetic actuator 306 (as shown in Figure 3).

Figure 4B illustrates what occurs when magnetic actuator 306 senses a current overload condition or when magnetic actuator 306 is signaled by control device 302 to open vacuum interrupter 310. First, signal 314 has an opposite polarity from the "closed" current signal discussed with reference in Figure 4A. Also, signal 314 is of sufficient value to momentarily cancel the strength of the permanent magnets (not shown) and de-compress spring 301, thus separating stationary contact 402 and moving contact 401. As insulated pushrod 303 and moveable shaft 311 move in upward direction 405, vacuum interrupter 310 opens the connection between busbar 204 and busbar 109, thus interrupting the current flow to transformer winding 103 and/or high voltage output bushing 315. Stationary contact 402 and moving contact 401 are held in the open position by permanent magnets (not shown) of magnetic actuator 306. Alternatively, magnetic actuator 306 may be actuated to open vacuum interrupter 310, independent of an overload condition, via control device 302. In this way, control device 302 may be used to purposely interrupt the current flow to transformer winding 103 or high voltage output bushing 315. Such an interruption event may be conducted to protect transformer winding 103 or the downstream distribution system from current overload conditions, or for testing and maintenance purposes, for example. In one embodiment, control device 302 may be remotely electrically operated a safe distance from vacuum interruption device 106. Once the interruption condition is removed, magnetic actuator 306 moves movable contact 401 in downward direction 404 with movable shaft 311, thus closing the circuit between busbar 204 and transformer winding 103, as shown in Figure 4A.

Although the present invention has been described in relation to particular embodiments, many other variations and modifications and other uses will become apparent to those skilled in the art. For example, although the present invention was described in the context of a pad-mounted three-phase distribution transformer system, it should be appreciated that the present invention may be used in any type of transformer system, including a single-phase power transformer, for example. In addition, although the present invention has been described as being used in liquid-filled transformers, it should be appreciated that it also may be used in dry transformers. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

What Is Claimed Is:

1. An electrical transformer device, comprising: at least one electrical transformer winding; and at least one interrupting device coupled to said at least one electrical transformer winding, wherein said interrupting device includes a vacuum enclosure.

2. The device of claim 1 , wherein said interrupting device further comprises electrical contacts connected in series with said electrical transformer winding, wherein said electrical contacts reside within said vacuum enclosure, and wherein said electrical contacts are movable between an open and a closed position.

3. The device of claim 2, wherein said interrupting device further comprises a linear shaft movable by a magnetic actuator, wherein said linear shaft is coupled to one of said electrical contacts such that movement of said linear shaft by said magnetic actuator cause said electrical contacts to move from said closed position to said open position.

4. The device of claim 3, wherein said magnetic actuator is activated by an input signal.

5. The device of claim 4, wherein said input signal is an electrical current.

6. The device of claim 4, wherein said input signal is an electrical voltage.

7. The device of claim 1, wherein said electrical transformer device includes a fluid-filled enclosure, and wherein said interrupting device is immersed within said fluid-filled enclosure.

8. A method for interrupting electrical power to an electrical transformer device, comprising the steps of: providing said electrical power to said electrical transformer device; measuring said electrical power; and disconnecting said electrical power from said electrical transformer device in a vacuum device when said electrical power exceeds a predetermined value.

9. The method of claim 8, further comprising disconnecting said electrical power from said electrical transformer device based on a control signal.

10. The method of claim 8, wherein said electrical transformer device includes a fluid-filled enclosure.

11. An electrical transformer device, comprising: at least one input terminal; at least one output terminal; and at least one interrupting device coupled between said at least one input terminal and said at least one output terminal , wherein said interrupting device includes a vacuum enclosure.

12. The device of claim 11, wherein said interrupting device further comprises a first electrical contact connected in series with said input terminal and a second electrical contact connected in series with said output terminal,- wherein said electrical contacts reside within said vacuum enclosure, and wherein said electrical contacts are movable between an open and a closed position. lS. The device of claim 12, wherein said interrupting device further comprises a linear shaft movable by a magnetic actuator, wherein said linear shaft is coupled to said first electrical contact such that movement of said linear shaft by said magnetic actuator causes said first electrical contact to connect with said second electrical contact.

14. The device of claim 13, wherein said magnetic actuator is activated by an input signal.

15. The device of claim 14, wherein said input signal is an electrical current.

16. The device of claim 14, wherein said input signal is an electrical voltage.

17. The device of claim 11 , wherein said electrical transformer device includes a fluid-filled enclosure, and wherein said interrupting device is immersed within said fluid-filled enclosure.

18. An electrical distribution transformer device, comprising: at least one electrical transformer winding; and at least one interrupting device coupled to said at least one electrical transformer winding, wherein said interrupting device includes a linear shaft movable by a magnetic actuator, and wherein said linear shaft is coupled to one of a pair of electrical contacts located in a vacuum enclosure such that movement of said linear shaft by said magnetic actuator cause said pair of electrical contacts connected in series with said electrical transformer winding to open and interrupt power to said electrical transformer winding.

19. The device of claim 18, wherein said magnetic actuator is controlled by a control device that measures electrical current and/or voltage within said transformer device.

20. A power distribution system, comprising: an electrical distribution transformer device; at least one input terminal; at least one output terminal; and at least one interrupting device coupled between said at least one input terminal and said at least one output terminal, and coupled between said input terminal and said electrical distribution transformer, wherein said interrupting device includes a vacuum enclosure.

21. The device of claim 20, wherein said interrupting device further comprises a first electrical contact connected in series with said input terminal and a second electrical contact connected in series with said output terminal, wherein said electrical contacts reside within said vacuum enclosure, and wherein said electrical contacts are movable between an open and a closed position.

22. The device of claim 21 , wherein said interrupting device further comprises a linear shaft movable by a magnetic actuator, wherein said linear shaft is coupled to said first electrical contact such that movement of said linear shaft by said magnetic actuator causes said first electrical contact to connect with said second electrical contact.

23. The device of claim 22, wherein said magnetic actuator is activated by an input signal.

24. The device of claim 23, wherein said input signal is an electrical current.

25. The device of claim 23, wherein said input signal is an electrical voltage.

26. The device of claim 11 , wherein said electrical transformer device includes a fluid-filled enclosure, and wherein said interrupting device is immersed within said fluid- filled enclosure.